PPGA 503 Midterm UPDATED ACTUAL
Questions and CORRECT Answers
Statistics - CORRECT ANSWER - the body of methods for obtaining and analyzing data;
a summary of the sample data.
They provide methods for:
• Design: Planning how to gather data for a research study to investigate questions of interest to
us.
• Description: summarizing data obtained in the study
• Inference: making predictions based on data, to help us deal with uncertainty in an objective
manner
Observational Studies - CORRECT ANSWER - captures a characteristic of interest;
Collect data by merely observing outcomes [though be wary of OVB - omitted variable bias,
caused by selection bias]
Data - CORRECT ANSWER - the collection of observations that interest us
Population - CORRECT ANSWER - total set of subjects of interest in a study
Parameter - CORRECT ANSWER - A numerical summary of the population
Sample - CORRECT ANSWER - the subset of the population on which the study collects
data.
Descriptive statistics - CORRECT ANSWER - summarize the information in a collection
of data;
Two main characteristics for numeric data are:
•Central tendency (describing typical observations)
•Dispersion (describing variation across observations)
, Inferential statistics - CORRECT ANSWER - Provide predictions about a population,
based on data from a sample of that population
Variable - CORRECT ANSWER - A characteristic that can vary in value among subjects
in a sample or population. The values the variable can take form the measurement scale.
Interval variable - CORRECT ANSWER - has meaningful numeric distance between
levels.
• A discrete variable: its possible values form a set of separate numbers [number of siblings = 0,
1, 2, 3...]
• A continuous variable: can take an infinite continuum of possible real number values [height in
cm = 183.2192.... ]
Categorical variable - CORRECT ANSWER - does not have a natural or meaningful
numeric distance between levels.
• An ordinal variable has a natural order [how do you feel about this class = excited, neutral,
terrified]
• A nominal variable has no clear high or low [type of transportation = bus, car, bike, walk]
Dependent variable (DV) - CORRECT ANSWER - the outcome variable you are trying to
explain.
Independent variable (IV) - CORRECT ANSWER - the variable(s) that causes change in
the DV.
Sampling Error - CORRECT ANSWER - The error that occurs when we use a statistic
based on a sample to predict the value of a population parameter
Sampling bias - CORRECT ANSWER - Occurs from using nonprobability samples, such
as the selection bias inherent in volunteer samples
Questions and CORRECT Answers
Statistics - CORRECT ANSWER - the body of methods for obtaining and analyzing data;
a summary of the sample data.
They provide methods for:
• Design: Planning how to gather data for a research study to investigate questions of interest to
us.
• Description: summarizing data obtained in the study
• Inference: making predictions based on data, to help us deal with uncertainty in an objective
manner
Observational Studies - CORRECT ANSWER - captures a characteristic of interest;
Collect data by merely observing outcomes [though be wary of OVB - omitted variable bias,
caused by selection bias]
Data - CORRECT ANSWER - the collection of observations that interest us
Population - CORRECT ANSWER - total set of subjects of interest in a study
Parameter - CORRECT ANSWER - A numerical summary of the population
Sample - CORRECT ANSWER - the subset of the population on which the study collects
data.
Descriptive statistics - CORRECT ANSWER - summarize the information in a collection
of data;
Two main characteristics for numeric data are:
•Central tendency (describing typical observations)
•Dispersion (describing variation across observations)
, Inferential statistics - CORRECT ANSWER - Provide predictions about a population,
based on data from a sample of that population
Variable - CORRECT ANSWER - A characteristic that can vary in value among subjects
in a sample or population. The values the variable can take form the measurement scale.
Interval variable - CORRECT ANSWER - has meaningful numeric distance between
levels.
• A discrete variable: its possible values form a set of separate numbers [number of siblings = 0,
1, 2, 3...]
• A continuous variable: can take an infinite continuum of possible real number values [height in
cm = 183.2192.... ]
Categorical variable - CORRECT ANSWER - does not have a natural or meaningful
numeric distance between levels.
• An ordinal variable has a natural order [how do you feel about this class = excited, neutral,
terrified]
• A nominal variable has no clear high or low [type of transportation = bus, car, bike, walk]
Dependent variable (DV) - CORRECT ANSWER - the outcome variable you are trying to
explain.
Independent variable (IV) - CORRECT ANSWER - the variable(s) that causes change in
the DV.
Sampling Error - CORRECT ANSWER - The error that occurs when we use a statistic
based on a sample to predict the value of a population parameter
Sampling bias - CORRECT ANSWER - Occurs from using nonprobability samples, such
as the selection bias inherent in volunteer samples
